1. Field of the Invention
The present invention relates to a printing apparatus for printing directly on a box shaped object carried along a carrier passage.
2. Description of the Background Art
In a case of printing four sides of a box shaped object such as a cardboard box directly at a carrier passage along which the box shaped object is carried, it has been necessary conventionally to stop the box shaped object by a stopper provided at a predetermined position on the carrier passage in order to print on one side of the box shaped object at that position, then to turn the box shaped object by 90.degree. manually in order to print on another side of the box shaped object, and so on.
However, this type of a conventional printing apparatus requires cumbersome manual operations for turning the box shaped object to be carried out by an attendant worker, so that the efficiency of the printing process has inevitably been low.
Also, it has been possible conventionally to provide two printers on both sides of the carrier passage such that two opposing sides of the box shaped object can be printed simultaneously by stopping the box shaped object by a stopper provided at a predetermined position on the carrier passage, then to turn the box shaped object by 90.degree. manually in order to print on another two opposing sides of the box shaped object simultaneously.
However, this type of a conventional printing apparatus also requires cumbersome manual operation for turning the box shaped object to be carried out by an attendant worker, so that the efficiency of the printing process has also inevitably been low. Moreover, in this type of a conventional printing apparatus, when the adjacent sides of the box shaped object have different lengths, it is necessary to adjust the width of the carrier passage according to a size of the box shaped object while turning the box shaped object by 90.degree.. Furthermore, in this type of a conventional printing apparatus, the printing positions by the printers are fixed, so that it has been impossible to automatically provide the printing at desired positions for a number of box shaped objects of different sizes carried along the carrier passage in an arbitrary order.
Also, it has been possible conventionally to provide a turning mechanism at a predetermined position on the carrier passage such that one side of the box shaped object is printed by stopping the box shaped object by a stopper provided at a predetermined position on the carrier passage, then another side of the box shaped object is printed by turning the box shaped object by 90.degree. with the turning mechanism on the carrier passage, and so on.
However, this type of a conventional printing apparatus has a drawback of being quite complicated in configuration and expensive in cost because of the additional feature of the turning mechanism. Moreover, in this type of a conventional printing apparatus, the size of the box shaped object that can be handled by a particular turning mechanism is limited within a certain range, so that it has been necessary to change the turning mechanism according to the size of the box shaped object to be handled in order to deal with box shaped objects of different sizes.